Crystal reports 11 : blank field bombs the report

Question

I'm creating a invoice crystal report for sage mas 500 AR module. In it, I'm attempting to add the tarinvoice.balance field with the following formula:

if {tarPrintInvcHdrWrk.Posted} = 1 then 
    ToText({tarInvoice.Balance})

I'm assuming that when the {tarPrintInvcHdrWrk.Posted} = 1 conditional statement holds FALSE, it doesn't attempt to pull the invoice field because when I remove the formula from the report, the form displays correctly without it.

When the conditional statement renders true in the report, the balance fields behaves correctly. However, with the formula renders FALSE in the CR form, the entire crystal report bombs and displays blank. Any ideas why or what I'm doing wrong?

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Just tried setting everything to zero and the report still bombs. I'm starting to think its more of a query error in the report. I wish there was a way to exclude the field in the query when posted = 0.

With tarinvoice.balance removed when the posted = 0, the report works fine.
With tarinvoice.balance included and posted = 1, report works fine.

With tarinvoice.balance included and posted =0, report bombs.

Solution

I believe the conditional statement fails immediately if you encounter a NULL, so your formula needs to test IsNull({tarPrintInvcHdrWrk.Posted}) before it tests equality with "1".